How Purple Became the Color of Choice for Electronic Toll Collection Traffic Control Signs

For centuries, the power of color to capture people’s attention has been used to convey information and instructions. For example, it’s no coincidence that stop signs are universally colored red. Scarlet shades stand out from most backgrounds and command a viewer’s attention. Bright yellows have similar effects, hence their traditional use for traffic control signs like those near schools and railroad crossings.

The choice of the color purple to designate lanes for auto-paying toll road lanes began back in 1991, when seven toll collection agencies from New Jersey, New York, and Pennsylvania created an alliance known as the E-ZPass IAG. One of the organization’s first duties was to choose a way to designate the auto-paying lanes, known from then on by the term E-ZPass. At the time there were three colors held in reserve by the MUTCD (Manual on Uniform Traffic Control Devices). Purple was one of these and it offered the highest contrast level of the available choices, so it was selected to designate these lanes. Specifically, the final choice is known as PMS (Pantone® Matching System®) 259 Purple.

Use of the color choice spread, until today 24 agencies in 13 different states have joined the IAG and adopted PMS 259 Purple for their Electronic Toll Collection lanes. Recognizing the utility value and widespread acceptance of the tone, the Federal Highway Administration on January 2, 2008 released a Notice of Proposed Amendments to the MUTCD, in which it supported designation of the color purple for use with electronic toll collection signs.

In the 2009 MUTCD, this policy became the law of the land. All signs designating electronic toll paying lanes must fit within one of these two guidelines:

1. A purple background with a white outline
2. A pictograph design with a background color other than purple, with a purple underlay panel and a contrasting white border.

Use of this design for traffic control signs and traffic delineators is expected to facilitate smooth vehicle flow and eliminate driver confusion as to what lane to take if they use Electronic Toll Collection.